1. Field of the Invention
The present invention relates to an illumination optical system used in an exposure apparatus for manufacturing semiconductor and liquid crystal display substrates to illuminate a plurality of areas on a mask, and a scanning exposure apparatus using the illumination optical system.
2. Related Background Art
FIGS. 1 and 2 show the arrangement of a conventional illumination optical apparatus. FIGS. 1 and 2 are sectional views respectively taken along the X-Z plane and the Y-Z plane in the X-Y-Z orthogonal coordinate system having an optical axis as the Z-axis.
The illumination optical apparatus shown in FIGS. 1 and 2 includes a light source 201 such as a mercury-arc lamp. The light source 201 is positioned at the first focal position of an elliptical mirror 202. A light beam emitted from the light source 201 is focused by the elliptical mirror 202 to form a light source image at a second focal position E of the elliptical mirror 202.
A light beam from this light source image is incident on a collimation lens 203 to be collimated. Thereafter, the parallel light beam is incident on an optical integrator 204 as a multiple light source forming means (this incident plane is indicated by "F"). As shown in FIG. 3, a lens element 207 constituting the optical integrator 204 has a rectangular cross-section almost similar to the shape of an illumination area. As shown in FIGS. 1 and 2, the optical integrator 204 is constituted by a plurality of lens elements 207 arranged vertically and horizontally to have an almost square cross-section as a whole.
The parallel light beam incident on the optical integrator 204 is focused to form a plurality of light source images at an exit plane G of the optical integrator 204. Light beams from these light source images are incident on a condenser lens 206 via an aperture stop 205 positioned immediately behind the exit plane G. The light beams from the light source images uniformly illuminate a rectangular illumination area on a mask surface R in a superposed state.